It is well known in the art to cure, i.e., vulcanize, green tires using a tire press. Typically tire presses use molds comprising top and bottom mold halves, within which the green tire is cured. The tire press includes devices for opening the mold, that is, lifting the top mold half from the bottom mold half, loading the green tire into the bottom mold half, and closing the top mold half upon the bottom mold half, thereby encasing the green tire within the tire mold. Heat mediums, such as steam, are then transferred to the mold from the outside of the mold as well as from the inside. A tire bladder is inserted inside the mold and the green tire and is used both to cure and to shape the green tire. Once the green tire is cured, the tire press then opens, that is, lifts the top mold from the bottom mold, revealing a cured tire which is then unloaded from the tire press. This cycle can be repeated as often as required.
One of the problems with this conventional type of tire press is that many devices are underutilized. The mold closing device, for example, closes the mold then sits idle while the green tire is cured. Only after the green tire is cured and unloaded and another green tire is loaded can the mold closing device be used again. The mold opening device, the green tire loading device and the cured tire unloading device are similarly underutilized. This means that the capital resources necessary for such tire presses are not being economically used.
Many attempts have been made to reduce these problems. For example, U.S. Pat. No. 3,932,079 to Legostave et al., discloses a tire vulcanizing apparatus that includes a series of vulcanizing presses arranged in a row. In short, Legostave et al. disclose an attempt at using a conventional tire press and moving it along rails over a line of tire molds. One of the problems associated with this apparatus are that the molds cannot be treated individually, but only in couplets of two. Another problem is that there is no provision for an independent loading device or a take-away conveyor. What is needed is a more flexible tire curing system.
U.S. Pat. No. 4,728,274 to Siegenthaler discloses a tire curing apparatus in which a number of mobile curing units are selectively moved along a loop circuit. This leads to a complex transport system for the mobile curing units.
U.S. Pat. No. 5,622,669 to Dailliez et al. discloses a tire vulcanization apparatus in which tire molds are transferred from a loading/unloading device into a chamber that receives several tire molds. The loading/unloading device is stationary. This apparatus makes it difficult to cure tires having different cure cycle times.
European Patent Application EP 0 510 332 A2 describes a mold changing apparatus including a row of mold stations, a moveable manipulator, and a mold preparing station provided within the row of mold stations. To use this apparatus, each mold must be carried by forklift or crane to each mold station. The manipulator combines the functions of opening/closing molds and loading/unloading tires. This combined use leads to operational inefficiencies.
The present invention provides methods and apparatuses for curing tires using a self-locking mold cure system with shared mold open, unload, load and close devices. The difficulties inherent in the art are therefore overcome in a way that is simple and efficient, while providing better and more advantageous results.